In order to resolve existing problems such as low efficiency, high cost and lack of technical resource in current maintenance, it is necessary to realize remote diagnosis for hydroelectric generating sets (HGSs). In this work, basing on the Service-Oriented Architecture (SOA) and Web Services technology, a SOA-oriented E-diagnostics system for HGSs (HGS-SES) is proposed, the framework of HGS-SES is constructed, a layout of the system’s hardware settings is described, the key modules of the system and a specific diagnostic procedure are given. HGS-SES makes rapid and convenient information transmission for services function and diagnosis decision-making, develops a dynamic network diagnostic platform for HGSs, and has broad prospects for farther research.